The present invention relates to a new and improved construction of testing apparatus for involute and helical gear teeth.
Generally speaking, the involute and helical gear teeth-testing apparatus of the present development is of the type comprising a rotatable chucking device for the test piece, a feeler device containing a feeler which can be moved along the tooth flanks of the test piece, and a respective drive for the chucking device and the feeler device. Also, there is provided a regulation device for at least one of such drives, and a mechanical transmission arrangement is disposed between the chucking device and the feeler device. A displacement path transducer or displacement pickup is arranged between two elements of the transmission, this pickup or transducer measuring the relative movements of both transmission elements. An electrical circuit serves, on the one hand, to infeed the measuring signals of the displacement path transducer to the regulation device and, on the other hand, these measuring signals are superimposed upon the measuring signals of the feeler device.
With a heretofore known testing apparatus of this species, as disclosed in German Patent Publication No. 2,747,863, the mechanical transmission, which interconnects the chucking device with the feeler device, is interrupted at one location, and thus, is divided into two partial chains. One of these partial chains is only connected with the chucking device for the test piece and its drive, whereas the other partial chain only is connected with the feeler device and its drive. The displacement pickup or transducer is arranged between both of the elements of the transmission which neighbor the separation location. Consequently, the entire transmission is load-relieved from the drive of the test piece, and thus, fulfills only a pure measuring function. There thus should be obtained the result that also in the case of large and heavy test pieces there can be extremely accurately measured involute and/or helical tooth errors, in contrast to older prior art testing devices provided for the same purpose where the chucking device for the test piece is connected with the feeler device by means of a totally rigid transmission. With such prior art devices there is provided only a single drive which drives, by means of the transmission, both the chucking device for the test piece and also the feeler device. If such older constructions of testing devices are employed for measuring test pieces having large moment of inertia, then frequently oscillations arise which, for instance, are excited by a stick-slip effect and falsify the measurement results to a point where they no longer can serve any useful purpose.
Up to a certain point such disturbing side effects can be avoided with the described state-of-the-art testing device of the previously mentioned type, but nonetheless with such testing device appreciable oscillations still arise at least at the start of each measuring cycle when the test piece is accelerated to the desired generating velocity. Due to these appreciable oscillations at least part of the measurement results are unusable, since the relative movements of the elements of the transmission arranged at both sides of the displacement path transducer, by virtue of such oscillations, exceed the measurement range of the displacement path transducer, and thus, also the possibility of fault compensation.